From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Wed, 23 Oct 2019 12:28:57 +0200
Subject: [PATCH 08/10] x86/tsx: Add "auto" option to the tsx= cmdline
parameter
Patch-mainline: v5.4-rc8
Git-commit: 7531a3596e3272d1f6841e0d601a614555dc6b65
References: bsc#1139073, CVE-2019-11135
commit 7531a3596e3272d1f6841e0d601a614555dc6b65 upstream
Platforms which are not affected by X86_BUG_TAA may want the TSX feature
enabled. Add "auto" option to the TSX cmdline parameter. When tsx=auto
disable TSX when X86_BUG_TAA is present, otherwise enable TSX.
More details on X86_BUG_TAA can be found here:
https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html
[ bp: Extend the arg buffer to accommodate "auto\0". ]
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/x86/kernel/cpu/tsx.c | 7 ++++++-
2 files changed, 9 insertions(+), 1 deletion(-)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4496,6 +4496,9 @@
update. This new MSR allows for the reliable
deactivation of the TSX functionality.)
+ auto - Disable TSX if X86_BUG_TAA is present,
+ otherwise enable TSX on the system.
+
Not specifying this option is equivalent to tsx=off.
See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
--- a/arch/x86/kernel/cpu/tsx.c
+++ b/arch/x86/kernel/cpu/tsx.c
@@ -75,7 +75,7 @@ static bool __init tsx_ctrl_is_supported
void __init tsx_init(void)
{
- char arg[4] = {};
+ char arg[5] = {};
int ret;
if (!tsx_ctrl_is_supported())
@@ -87,6 +87,11 @@ void __init tsx_init(void)
tsx_ctrl_state = TSX_CTRL_ENABLE;
} else if (!strcmp(arg, "off")) {
tsx_ctrl_state = TSX_CTRL_DISABLE;
+ } else if (!strcmp(arg, "auto")) {
+ if (boot_cpu_has_bug(X86_BUG_TAA))
+ tsx_ctrl_state = TSX_CTRL_DISABLE;
+ else
+ tsx_ctrl_state = TSX_CTRL_ENABLE;
} else {
tsx_ctrl_state = TSX_CTRL_DISABLE;
pr_err("tsx: invalid option, defaulting to off\n");